The Resonating Star Gyroscope: A Novel Multiple-Shell Silicon Gyroscope With Sub-5 deg/hr Allan Deviation Bias Instability

We report on the design, fabrication and characterization of a novel multiple-shell silicon vibratory microgyroscope. The resonating star gyroscope (RSG) is formed as a merged superposition of two square shells, yielding in-plane flexural modes that are utilized to sense rotation along the normal axis. The first prototypes of the single-shell RSG were implemented with 65 mum thick trench-refilled polysilicon structural material using the HARPSS process. These devices exhibited open-loop rate sensitivity of approximately 800 muV/deg/s. Despite high-aspect ratio sensing gaps, the device yielded poor sensitivity caused by low resonant-mode quality factors. To alleviate the Q TED losses caused by the inevitable formation of voids in trench-refilled structural material, the RSG was implemented in (111) single crystalline silicon. A 2.5-mm multiple-shell RSG was fabricated in 40 mum-thick SOI device layer using a simple two-mask process. Multiple-shells enable a higher operating frequency and larger resonant mass, essential components for reducing the mechanical noise floor of the sensor. Experimental data of a high-Q (111) multiple-shell prototype indicates sub-5 deg/hr Brownian noise floor, with a measured Allan deviation bias drift of 3.5 deg/hr. The gyroscope exhibits an open-loop rate sensitivity of approximately 16.7 mV/deg/s in vacuum.

[1]  Barry Gallacher,et al.  Principles of a three-axis vibrating gyroscope , 2001 .

[2]  J. Bernstein,et al.  A micromachined comb-drive tuning fork rate gyroscope , 1993, [1993] Proceedings IEEE Micro Electro Mechanical Systems.

[3]  Reza Abdolvand,et al.  Quality factor in trench-refilled polysilicon beam resonators , 2006, Journal of Microelectromechanical Systems.

[4]  Xiaoji Niu,et al.  Analysis and Modeling of Inertial Sensors Using Allan Variance , 2008, IEEE Transactions on Instrumentation and Measurement.

[5]  Sukhan Lee,et al.  Micromachined inertial sensors , 1999, Proceedings 1999 IEEE/RSJ International Conference on Intelligent Robots and Systems. Human and Environment Friendly Robots with High Intelligence and Emotional Quotients (Cat. No.99CH36289).

[6]  Guohong He,et al.  A single-crystal silicon vibrating ring gyroscope , 2002, Technical Digest. MEMS 2002 IEEE International Conference. Fifteenth IEEE International Conference on Micro Electro Mechanical Systems (Cat. No.02CH37266).

[7]  Yong-Kweon Kim,et al.  Vacuum packaged low noise gyroscope with sub mdeg/s//spl radic/Hz resolution , 2005, 18th IEEE International Conference on Micro Electro Mechanical Systems, 2005. MEMS 2005..

[8]  D. Janiaud,et al.  A new analog oscillator electronics applied to a piezoelectric vibrating gyro , 2004, Proceedings of the 2004 IEEE International Frequency Control Symposium and Exposition, 2004..

[9]  G. Schmidt,et al.  Inertial sensor technology trends , 2001 .

[10]  B.E. Boser,et al.  An integrated, vertical-drive, in-plane-sense microgyroscope , 2003, TRANSDUCERS '03. 12th International Conference on Solid-State Sensors, Actuators and Microsystems. Digest of Technical Papers (Cat. No.03TH8664).

[11]  M. W. Putty.  A Maicromachined vibrating ring gyroscope , 1994 .

[12]  O. Schwarzelbach,et al.  New Approach for Frequency Matching of Tuning Fork Gyroscopes by Using a Nonlinear Driving Concept , 2001 .

[13]  F. Ayazi,et al.  High Performance Matched-Mode Tuning Fork Gyroscope , 2006, 19th IEEE International Conference on Micro Electro Mechanical Systems.

[14]  F. Ayazi,et al.  High aspect-ratio combined poly and single-crystal silicon (HARPSS) MEMS technology , 2000, Journal of Microelectromechanical Systems.

[15]  S. Sherman,et al.  Single-chip surface micromachined integrated gyroscope with 50°/h Allan deviation , 2002, IEEE J. Solid State Circuits.

[16]  R. Neul,et al.  Micromachined Angular Rate Sensors for Automotive Applications , 2007, IEEE Sensors Journal.

[17]  B. Vigna,et al.  Future of MEMS: An industry point of view , 2006, International Conference on Thermal, Mechanial and Multi-Physics Simulation and Experiments in Micro-Electronics and Micro-Systems.

[18]  F. Ayazi,et al.  A 0.1°/HR bias drift electronically matched tuning fork microgyroscope , 2008, 2008 IEEE 21st International Conference on Micro Electro Mechanical Systems.

[19]  Gary K. Fedder,et al.  A DRIE CMOS-MEMS gyroscope , 2002, Proceedings of IEEE Sensors.

[20]  F. Ayazi,et al.  The resonating star gyroscope , 2005, 18th IEEE International Conference on Micro Electro Mechanical Systems, 2005. MEMS 2005..

[21]  K. Najafi,et al.  A HARPSS polysilicon vibrating ring gyroscope , 2001 .

[22]  Andrei M. Shkel,et al.  NEW ARCHITECTURAL DESIGN OF A TEMPERATURE ROBUST MEMS GYROSCOPE WITH IMPROVED GAIN-BANDWIDTH CHARACTERISTICS , 2008 .

[23]  J. Marek.  MEMS Technology- from Automotive to Consumer , 2007, 2007 IEEE 20th International Conference on Micro Electro Mechanical Systems (MEMS).

[24]  B. Legrand,et al.  Clamped-Clamped Beam Micro-Mechanical Resonators in Thick-Film Epitaxial Polysilicon Technology , 2002, 32nd European Solid-State Device Research Conference.